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  • 101.
    Qin, Jian
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Laurent, S.
    Jo, Y. S.
    Roch, A.
    Mikhaylova, M.
    Bhujwalla, Z. M.
    Muller, R. N.
    Mohammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    A high-performance magnetic resonance imaging T2 contrast agent2007Ingår i: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 19, nr 14, s. 1874-1878Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A high-performance magnetic resonance imaging T-2 contrast agent has been prepared via phase transfer of hydrophobic superparamagnetic iron oxide nanoparticles (SPIONs) to an aqueous solution by using Pluronic F127 copolymers. As seen in the figure, a hierarchical structure of the surface coating is formed and proven to be a crucial characteristic to enhance not only water dispersibility, but also the efficacy as a T-2 contrast agent.

  • 102.
    Raza, Rizwan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Abbas, Ghazanfar
    Wang, Xiaodi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Ma, Ying
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Electrochemical study of the composite electrolyte based on samaria-doped ceria and containing yttria as a second phase2011Ingår i: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 188, nr 1, s. 58-63Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this study is to develop new oxide ionic conductors based on nanocomposite materials for an advanced fuel cell (NANOCOFC) approach. The novel two phase nanocomposite oxide ionic conductors, Ce0.8Sm0.2O2-delta (SDC)-Y2O3 were synthesized by a co-precipitation method. The structure and morphology of the prepared electrolyte were investigated by means of X-ray diffraction (XRD) and high resolution scanning electron microscopy (HRSEM). XRD results showed a two phase composite consisting of yttrium oxide and samaria doped ceria and SEM results exhibited a nanostructure form of the sample. The yttrium oxide was used on the SDC as a second phase. The interface between two constituent phases and the ionic conductivities were studied with electrochemical impedance spectroscopy (EIS). An electrochemical study showed high oxide ion mobility and conductivity of the Y2O3-SDC two phase nanocomposite electrolytes at a low temperature (300-600 degrees C). Maximum conductivity (about 1.0 S cm(-1)) was obtained for the optimized Y2O3-SDC composite electrolyte at 600 degrees C. It is found that the nanocomposite electrolytes show higher conductivities with the increased concentration of yttrium oxides but decreases after reaching a certain level. A high fuel cell performance, 0.75 W cm(-2), was achieved at 580 degrees C.

  • 103.
    Raza, Rizwan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Liu, Qinghua
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Nisar, Jawad
    Wang, Xiaodi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Ma, Ying
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    ZnO/NiO nanocomposite electrodes for low-temperature solid oxide fuel cells2011Ingår i: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 13, nr 9, s. 917-920Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    ZnO/NiO nanocomposite electrodes have successfully been developed using a cost-effective method, and for the first time used in LT-SOFCs at 300-600 degrees C. They exhibit high conductivity and a dual catalytic functionality in both the cathode and the anode for the electrochemical reduction of O(2) and oxidation of H(2), respectively. An excellent fuel cell performance, e.g. a maximum power density of 1107 W cm(-2), has been shown for a symmetrical fuel cell that contained ZnO/NiO nanocomposite electrodes at 500 degrees C. To our knowledge, to date this is by far the highest power density achieved at this temperature.

  • 104.
    Raza, Rizwan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Ma, Ying
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Wang, Xiaodi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Liu, Xiangrong
    Zhu, Bin
    Study on Nanocomposites Based on Carbonate@Ceria2010Ingår i: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 10, nr 2, s. 1203-1207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanocomposites based on the ceria-carbonate composite have demonstrated as electrolytes in development of successful 300-600 oC fuel cell technology. In this paper, the nanocomposite electrolyte based on carbonate@SDC (SDC: samarium doped ceria) was directly synthesized from the co-precipitation method and characterized by XRD, SEM, TEM, BET, etc. It was proved that the carbonate@SDC was a two-phase material with average particle size about 14.5 nm (S-BET) and crystalline size (D-XRD) ranged from 12 to 14 nm. When the carbonate@SDC electrolyte was used to fabricate single SOFC, the cell shows remarkable performance with maximum power density 1000-1180 mW/cm2 at low temperature (300-550 oC).

  • 105.
    Raza, Rizwan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Wang, Xiaodi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Ma, Ying
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Haung, Yizhong
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Enhancement of conductivity in ceria-carbonate nanocomposites for LTSOFCs2009Ingår i: Journal of nano research, ISSN 1662-5250, Vol. 6, s. 197-204Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work first explores high resolution transmission electron microscopy (TEM) to determine the interfacial regions and provide experimental evidences for interfaces between the SDC and carbonate constituent phases of the SD-carbonate two-phase composites to further investigate the superionic conduction mechanism in the ceria-carbonate composite systems and enhancement of conductivity. Schober first reported interfacial superionic conduction in ceria-based composites but without direct experimental proofs. Such superionic conduction mechanism remains unknown. Especially, in the nano-scale, this region is trifle to be detected.

  • 106.
    Raza, Rizwan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Wang, Xiaodi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Ma, Ying
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Liu, Xiangrong
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Improved ceria-carbonate composite electrolytes2010Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 35, nr 7, s. 2684-2688Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It has been successfully demonstrated that the fuel cells using the ceria-carbonate composite as electrolytes have achieved excellent performances of 200-1150 W/cm(2) at 300-600 degrees C. Previously it was reported these ceria-carbonate composite electrolytes have been prepared with two-step processes: step 1, prepare ion-doped ceria which was prepared usually through the wet-chemical co-precipitation process; step 2, mixing the doped ceria with carbonates in various compositions. We first report here to prepare the SDC-carbonate composites within one-step chemical co-precipitation process, i.e. mixing carbonates and preparing the SDC in the same process. The one-step process has provided a number of advantages: (i) to reduce the involved preparation processes to enhance the production, to make the produced materials in good quality control, more homogenous composites microstructure; (ii) as results, these composites showed also different microstructures and electrical properties. It has significantly improved the ceria-carbonate conductivities and cause the superionic conduction at much lower temperatures; (iii) to reduce manufacturing costs also.

  • 107.
    Raza, Rizwan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Wang, Xiaodi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Ma, Ying
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    A nanostructure anode (Cu0.2Zn0.8) for low-temperature solid oxide fuel cell at 400-600 oC2010Ingår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 195, nr 24, s. 8067-8070Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We developed a new nickel-free anode for a low-temperature solid oxide fuel cell (LTSOFC) that demonstrated an outstanding electrochemical output of 1000 mW cm(-2) at 550 degrees C. The nanostructure anode had good conductivity and was compatible with cerium oxide-based electrolytes. The performance of a single cell was comparable and or better than those using standard Ni-YSZ and Ni-SDC electrodes (anode). It may have applications for hydrocarbon-based fuel for preventing carbon deposition and replacing nickel in the anode of LTSOFCs.

  • 108. Rieth, M.
    et al.
    Boutard, J. L.
    Dudarev, S. L.
    Ahlgren, T.
    Antusch, S.
    Baluc, N.
    Barthe, M. -F
    Becquart, C. S.
    Ciupinski, L.
    Correia, J. B.
    Domain, C.
    Fikar, J.
    Fortuna, E.
    Fu, C. -C
    Gaganidze, E.
    Galan, T. L.
    Garcia-Rosales, C.
    Gludovatz, B.
    Greuner, H.
    Heinola, K.
    Holstein, N.
    Juslin, N.
    Koch, F.
    Krauss, W.
    Kurzydlowski, K. J.
    Linke, J.
    Linsmeier, Ch.
    Luzginova, N.
    Maier, H.
    Martinez, M. S.
    Missiaen, J. M.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Munoz, A.
    Muzyk, M.
    Nordlund, K.
    Nguyen-Manh, D.
    Norajitra, P.
    Opschoor, J.
    Pintsuk, G.
    Pippan, R.
    Ritz, G.
    Romaner, L.
    Rupp, D.
    Schaeublin, R.
    Schlosser, J.
    Uytdenhouwen, I.
    van der Laan, J. G.
    Veleva, L.
    Ventelon, L.
    Wahlberg, S.
    Willaime, F.
    Wurster, S.
    Yar, M. A.
    Review on the EFDA programme on tungsten materials technology and science2011Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 417, nr 1-3, s. 463-467Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    All the recent DEMO design studies for helium cooled divertors utilize tungsten materials and alloys, mainly due to their high temperature strength, good thermal conductivity, low erosion, and comparably low activation under neutron irradiation. The long-term objective of the EFDA fusion materials programme is to develop structural as well as armor materials in combination with the necessary production and fabrication technologies for future divertor concepts. The programmatic roadmap is structured into four engineering research lines which comprise fabrication process development, structural material development, armor material optimization, and irradiation performance testing, which are complemented by a fundamental research programme on "Materials Science and Modeling". This paper presents the current research status of the EFDA experimental and testing investigations, and gives a detailed overview of the latest results on fabrication, joining, high heat flux testing, plasticity, modeling, and validation experiments.

  • 109. Rieth, M.
    et al.
    Dudarev, S. L.
    Gonzalez De Vicente, S. M.
    Aktaa, J.
    Ahlgren, T.
    Antusch, S.
    Armstrong, D. E. J.
    Balden, M.
    Baluc, N.
    Barthe, M. -F
    Basuki, W. W.
    Battabyal, M.
    Becquart, C. S.
    Blagoeva, D.
    Boldyryeva, H.
    Brinkmann, J.
    Celino, M.
    Ciupinski, L.
    Correia, J. B.
    De Backer, A.
    Domain, C.
    Gaganidze, E.
    García-Rosales, C.
    Gibson, J.
    Gilbert, M. R.
    Giusepponi, S.
    Gludovatz, B.
    Greuner, H.
    Heinola, K.
    Höschen, T.
    Hoffmann, A.
    Holstein, N.
    Koch, F.
    Krauss, W.
    Li, H.
    Lindig, S.
    Linke, J.
    Linsmeier, C.
    López-Ruiz, P.
    Maier, H.
    Matejicek, J.
    Mishra, T. P.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Muñoz, A.
    Muzyk, M.
    Nordlund, K.
    Nguyen-Manh, D.
    Opschoor, J.
    Ordás, N.
    Palacios, T.
    Pintsuk, G.
    Pippan, R.
    Reiser, J.
    Riesch, J.
    Roberts, S. G.
    Romaner, L.
    Rosiński, M.
    Sanchez, M.
    Schulmeyer, W.
    Traxler, H.
    Ureña, A.
    Van Der Laan, J. G.
    Veleva, L.
    Wahlberg, Sverker
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Walter, M.
    Weber, T.
    Weitkamp, T.
    Wurster, S.
    Yar, Mazher Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    You, J. H.
    Zivelonghi, A.
    Recent progress in research on tungsten materials for nuclear fusion applications in Europe2013Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 432, nr 1-3, s. 482-500Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The current magnetic confinement nuclear fusion power reactor concepts going beyond ITER are based on assumptions about the availability of materials with extreme mechanical, heat, and neutron load capacity. In Europe, the development of such structural and armour materials together with the necessary production, machining, and fabrication technologies is pursued within the EFDA long-term fusion materials programme. This paper reviews the progress of work within the programme in the area of tungsten and tungsten alloys. Results, conclusions, and future projections are summarized for each of the programme's main subtopics, which are: (1) fabrication, (2) structural W materials, (3) W armour materials, and (4) materials science and modelling. It gives a detailed overview of the latest results on materials research, fabrication processes, joining options, high heat flux testing, plasticity studies, modelling, and validation experiments.

  • 110. Rihtnesberg, D. B.
    et al.
    Almqvist, S.
    Wang, Q.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Yang, Xuran
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Besharat, Zahra
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Materialfysik, MF (Stängd 20120101).
    ZnO nanorods/nanoflowers and their applications2011Ingår i: Proc. - Int. NanoElectronics Conf., INEC, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Single-crystalline zinc oxide (ZnO) nanorods (NRs) have been synthesized through a chemical bath deposition method. Their diameter is about 80 nm, and their length range from 1 μm to 7 μm can be controlled by growth time. Formation of nanoflower arrays composed of nanorods has been also achieved utilizing a standard micro-fabrication technique. Two types of ZnO nanorods devices are detailed to demonstrate their optoelectronic applications.

  • 111. Salazar-Alvarez, G.
    et al.
    Qin, Jian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Sepelak, V
    Bergmann, I
    Vasilakaki, M
    Trohidou, N.
    Ardisson, D.
    Macedo, A.
    Mikhaylova, M.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Baro, D
    Nogues, J.
    Cubic versus spherical magnetic nanoparticles: The role of surface anisotropy2008Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, nr 40, s. 13234-13239Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The magnetic properties of maghemite (gamma-Fe2O3) cubic and spherical nanoparticles of similar sizes have been experimentally and theoretically studied. The blocking temperature, TB, of the nanoparticles depends on their shape, with the spherical ones exhibiting larger TB. Other low temperature properties such as saturation magnetization, coercivity, loop shift or spin canting are rather similar. The experimental effective anisotropy and the Monte Carlo simulations indicate that the different random surface anisotropy of the two morphologies combined with the low magnetocrystalline anisotropy of gamma-Fe2O3 is the origin of these effects.

  • 112.
    Saleemi, Mohsin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Användningen av en suspension omfattande mesoporösa kiseldioxidartiklar som värmeväxlarvätska2010Patent (Övrig (populärvetenskap, debatt, mm))
  • 113.
    Saleemi, Mohsin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Li, Shanghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Ma, Ying
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Wang, Xiaodi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Nikkam, Nader
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Haghighi, Ehsan Bitaraf
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Khodabandeh, Rahmatollah
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Palm, Björn
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Ceria Nanofluids for Efficient Heat Management2010Konferensbidrag (Refereegranskat)
  • 114.
    Saleemi, Mohsin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Li, Shanghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Johnsson, Mats
    Arrhenius Laboratory, Stockholm University.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Fabrication and Spark Plasma Sintering of Nanostructured Bismuth Telluride (Bi2Te3)2012Ingår i: 9Th European Conference On Thermoelectrics (ECT2011), American Institute of Physics (AIP), 2012, s. 115-118Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thermoelectric (TE) devices can harvest residual low-grade waste heat energy. Bismuth telluride (Bi2Te3) and its alloys are mostly used TE materials in the bulk form for making TE modules. We report a simple, fast and very high yield synthetic process for the bulk Bi2Te3 nanopowders with hexagonal plate like morphology. Spark plasma sintering (SPS) process has been optimized in order to preserve nanostructure while achieving a high compaction density of the pellets. Electron microscopy analysis was used to determine the effect of SPS parameters during compaction on the grain growth. Optimal conditions for the fabricated nanopowder was determined as 673 K, 70 MPa pressure with no holding time, which resulted in average lateral grain size in the range of 165-190 nm for a compact density of 98%. About 50% reduction of thermal conductivity was observed as compared to its bulk counterparts, revealing the feasibility of suggested route in the preservation of nanostructure and enhanced phonon scattering.

  • 115.
    Saleemi, Mohsin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Li, Shanghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Johnsson, Mats
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Synthesis, processing, and thermoelectric properties of bulk nanostructured bismuth telluride (Bi(2)Te(3))2012Ingår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, nr 2, s. 725-730Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bismuth telluride (Bi(2)Te(3)) is the best-known commercially used thermoelectric material in the bulk form for cooling and power generation applications at ambient temperature. However, its dimensionless figure-of-merit-ZT around 1 limits the large-scale industrial applications. Recent studies indicate that nanostructuring can enhance ZT while keeping the material form of bulk by employing an advanced synthetic process accompanied with novel consolidation techniques. Here, we report on bulk nanostructured (NS) undoped Bi(2)Te(3) prepared via a promising chemical synthetic route. Spark plasma sintering has been employed for compaction and sintering of Bi(2)Te(3) nanopowders, resulting in very high densification (>97%) while preserving the nanostructure. The average grain size of the final compacts was obtained as 90 +/- 5 nm as calculated from electron micrographs. Evaluation of transport properties showed enhanced Seebeck coefficient (-120 mu V K(-1)) and electrical conductivity compared to the literature state-of-the-art (30% enhanced power factor), especially in the low temperature range. An improved ZT for NS bulk undoped Bi(2)Te(3) is achieved with a peak value of similar to 1.1 at 340 K.

  • 116. Sertkol, M.
    et al.
    Koseoglu, Y.
    Baykal, A.
    Kavas, H.
    Bozkurt, A.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Microwave synthesis and characterization of Zn-doped nickel ferrite nanoparticles2009Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 486, nr 1-2, s. 325-329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microwave assisted combustion method was used to synthesize nanocrystalline ZnxNi1-xFe2O4 from a stoichiometric mixture of corresponding metal nitrates and urea powders. The structural, chemical and magnetic properties of Ni-Zn ferrite was determined by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (FTIR), vibrating sample magnetometry (VSM) and DC conductivity measurements. Results showed that the material was spinel structure with a high purity with an estimated crystallite size of similar to 20 nm by X-ray line profile fitting. TEM analysis showed necked near-spherical particles with an average size of similar to 20 nm, reflecting highly crystalline nature of these nanoparticles. Magnetic properties showed anomalities as the Zn doping level increased. This has been explained and attributed to the relative positions of Ni, Zn, and Fe ions in the crystal lattice.

  • 117. Sertkol, M.
    et al.
    Koseoglu, Y.
    Baykal, A.
    Kavas, H.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Synthesis and magnetic characterization of Zn0.7Ni0.3Fe2O4 nanoparticles via microwave-assisted combustion route2010Ingår i: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 322, nr 7, s. 866-871Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the synthesis of Zn0.7Ni0.3Fe2O4 nanoparticles via microwave assisted combustion route by using urea as fuel. XRD and FT-IR analyses confirm the composition and structure as spinel ferrite. The crystallite size estimated from XRD (16.4nm) and the magnetic core size(15.04nm) estimated from VSM agree well, while a slightly smaller magnetic diameterre reflects a very thin magnetically dead layer on the surface of the nanoparticles. Morphological investigation of the products was done by TEM which revealed the existence of irregular shapes such spherical, spherodial and polygon. Magnetization measurements performed on Zn0.7Ni0.3Fe2O4 nanoparticles showed that saturation was not attained at even in the high magnetic field. The sample shows superparamagnetic behavior at around the room temperature and ferromagnetic behavior below the blocking temperature which is measured as 284 K.

  • 118.
    Shahid, Robina
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Green Chemical Synthesis of II-VI Semiconductor Quantum Dots2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Nanotechnology is the science and technology of manipulating materials at atomic and molecular scale with properties different from bulk. Semiconductor QDs are important class of nanomaterials with unique physical and chemical properties owing to the quantum confinement effect. Size dependent optical properties make research on semiconductor QDs more attractive in the field of nanotechnology. Semiconductor QDs are usually composed of combination of elements from groups II–VI, III–V, or IV–VI of the periodic table. Group II-VI semiconductor QDs (ZnS, ZnSe, ZnO, CdSe, CdS) are most extensively studied systems, having bandgap which can be engineered through the variation of the material composition and size. Most common QDs are made of CdE (E=S, Se, Te) which are toxic. Recent environmental regulations restrict the use of toxic metals and therefore QDs containing nontoxic metals such as Zn are of great importance.

    The chemical synthesis of QDs involves different methods. Usually high temperature thermal decomposition of organometallic compounds in high boiling point organic solvents is used which needs long reaction time and involves complex synthesis procedures. New simpler and efficient synthetic routes with alternative solvents are required. Recently the synthesis of non-toxic QDs using green chemical routes is a promising approach receiving increasing attention.

    The aim of this Thesis is to develop novel routes for synthesis of semiconductor QDs employing green nanomaterial synthesis techniques. Therefore, in this work, we developed different green chemical routes mainly for the synthesis Zn-based QDs. Low temperature synthesis routes were developed for the synthesis of ZnS and ZnO QDs. Microwave irradiation was also used as efficient heating source which creates numerous nucleation sites in the solution, leading to the formation of homogeneous nanoparticles with small size and narrow size distribution. Different polar solvents with high MW absorption were used for synthesis of ZnS QDs. We also introduced ionic liquids as solvents in the synthesis of ZnS QDs using microwave heating. ILs are excellent reaction media for absorbing microwaves and are recognized as ‘green’ alternative to volatile and toxic organic solvents.

    For ZnS systems, the QDs produced by different methods were less than 5 nm in size as characterized by high-resolution transmission electron microscopy (HR-TEM). Selected area electron diffraction (SAED) patterns revealed that ZnS QDs synthesized by low temperature synthesis technique using conventional heating are of cubic crystalline phase while the QDs synthesized by using MW heating are of wurtzite phase. The optical properties were investigated by UV-Vis absorption spectrum and show a blue shift in absorption as compared to bulk due to quantum confinement effect. The photoluminescence (PL) spectra of ZnS QDs show different defect states related emission peaks and depend on different synthesis methods, high bandedge related emission is observed for ZnS QDs synthesized by using ionic liquids. ZnO QDs synthesized by low temperature route were found to be less than 4 nm in size and also show a blue shift in their absorption. The PL spectrum show bandedge related emission which is blue shifted compared with bulk with no emission originating from surface defect levels. The results show that QDs are of high crystalline quality with narrow size distribution. A comparative study of using conventional and MW heating in the synthesis of CdSe QDs was performed. The reactions involving microwave heating showed enhanced rates and higher yields.

    The developed methods involve all principles for green nanomaterials synthesis i.e. design of safer nanomaterials, reduced environmental impact, waste reduction, process safety, materials and energy efficiency.

  • 119.
    Shahid, Robina
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Gorlov, Mikhail
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    El-Sayed, Ramy
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Microwave assisted synthesis of ZnS quantum dots using ionic liquids2012Ingår i: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 89, s. 316-319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work we report results from microwave (MW) assisted synthesis of highly crystalline ZnS quantum dots (QDs) using ionic liquid (ILs) as MW absorbing medium. Two types of ionic liquids, imidazolium and phosphonium based, were used. The QDs are less than 5 nm in size and of wurtzite ZnS type, as characterized by high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) pattern. The optical properties were investigated by UV-vis absorption and show a blue shift in absorption as compared to bulk wurtzite ZnS due to quantum confinement effects. The photoluminescence (PL) spectra of the QDs show different trap state emissions.

  • 120.
    Shahid, Robina
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Soliman, Hesham M. A.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Fathy, M.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Novel lowtemperature route for large scale synthesis of ZnO QDsArtikel i tidskrift (Övrigt vetenskapligt)
  • 121.
    Shahid, Robina
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Microwave-assisted low temperature synthesis of wurtzite ZnS quantum dots2012Ingår i: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 187, s. 130-133Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work we report, for the first time, on microwave assisted synthesis of wurtzite ZnS quantum dots (QDs) in controlled reaction at temperature as low as 150 degrees C. The synthesis can be done in different microwave absorbing solvents with multisource or single source precursors. The QDs are less than 3 nm in size as characterized by transmission electron microscopy (TEM) using selected area electron diffraction (SAED) patterns to confirm the wurtzite phase of ZnS QDs. The optical properties were investigated by UV-Vis absorption which shows blue shift in absorption compared to bulk wurtzite ZnS due to quantum confinement effects. The photoluminescence (PL) spectra of QDs reveal point defects related emission of ZnS QDs.

  • 122.
    Shahid, Robina
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Soliman, Hesham M. A.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Low temperature synthesis of cubic phase zinc sulfide quantum dots2012Ingår i: Central European Journal of Chemistry, ISSN 1895-1066, E-ISSN 1644-3624, Vol. 10, nr 1, s. 54-58Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, we report on a new method for the synthesis of ZnS quantum dots (QDs). The synthesis was carried out at low temperature by a chemical reaction between zinc ions and freshly reduced sulfide ions in ethanol as reaction medium. Zinc chloride and elemental sulfur were used as zinc and sulfur sources, respectively and hydrazine hydrate was used as a strong reducing agent to convert elemental sulfur (S(8)) into highly reactive sulfide ions (S(2-)) which react spontaneously with zinc ions. This facile, less toxic, inexpensive route has a high yield for the synthesis of high quality metal sulfide QDs. Transmission electron microscopy (TEM) image analysis and selected area electron diffraction (SAED) reveal that ZnS QDs are less than 3 nm in diameter and are of cubic crystalline phase. The UV-Vis absorption spectrum shows an absorption peak at 253 nm corresponding to a band gap of 4.9 eV, which is high when compared to the bulk value of 3.68 eV revealing strong quantum confinement. PL emission transitions are observed at 314 nm and 439 nm and related to point defects in ZnS QDs.

  • 123. Shi, Jingwen
    et al.
    Karlsson, Hanna L.
    Johansson, Katarina
    Gogvadze, Vladimir
    Xiao, Lisong
    Li, Jiangtian
    Burks, Terrance
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Garcia-Bennett, Alfonso
    Uheida, Abdusalam
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Mathur, Sanjay
    Morgenstern, Ralf
    Kagan, Valerian E.
    Fadeel, Bengt
    Microsomal Glutathione Transferase 1 Protects Against Toxicity Induced by Silica Nanoparticles but Not by Zinc Oxide Nanoparticles2012Ingår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 6, nr 3, s. 1925-1938Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microsomal glutathione transferase 1 (MGST1) is an antioxidant enzyme located predominantly in the mitochondrial er membrane and endoplasmk reticulum and has been shown to protect cells from lipid peroxidation induced by a variety of cytostatic drugs and pro-oxidant stimuli. We hypothesized that MGST1 may also protect against nanomaterial-induced cytotoxicity through a specific effect on lipid peroxidation. We evaluated the induction of cytotoxicity and oxidative stress by TiO2, CeO2, SiO2, and ZnO in the human MCF-7 cell line with or without overexpression of MGST1. SiO2 and ZnO nanoparticles caused dose- and time-dependent toxicity, whereas no obvious cytotoxic effects were induced by nanoparticles of TiO2 and CeO2. We also noted pronounced cytotoxicity for three out of four additional SiO2 nanoparticles tested. Overexpression of MGST1 reversed the cytotoxicity of the main SiO2 nanoparticles tested and for one of the supplementary SiO2 nanoparticles but did not protect cells against ZnO-induced cytotoxic effects. The data point toward a role of lipid peroxidation In SiO2 nanoparticle-induced cell death. For ZnO nanoparticles, rapid dissolution was observed, and the subsequent interaction of Zn2+ with cellular targets is likely to contribute to the cytotoxic effects. A direct inhibition of MGST1 by Zn2+ could provide a possible explanation for the lack of protection against ZnO nanoparticles in this model. Our data also showed that SiO2 nanoparticle-induced cytotoxicity is mitigated in the presence of serum, potentially through masking of reactive surface groups by serum proteins, whereas ZnO nanoparticles were cytotoxic both In the presence and in the absence of serum.

  • 124.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Fabrication and Photoelectrochemical Applications of II-VI Semiconductor Nanomaterials2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this work we investigated fabrication of semiconductor nanomaterials and evaluated their potential for photo-chemical and photovoltaic applications. We investigated different II-VI semiconductor nanomaterial systems; (i) ZnO oriented nanowire arrays non-epitaxially grown from a substrate; and (ii) colloidal CdE (E=Te,Se,S) quantum structures synthesized by solution-based thermal decomposition of organo-metallic precursors.

    We have studied the synthesis of vertically aligned ZnO nanowire arrays (NWA), by a wet chemical process on various substrates. We have extended this method wherein nanofibers of poly-L-lactide act as a substrate for the radially oriented growth of ZnO nanowires. By combining the large surface area and the flexibility of the PLLA-ZnO hierarchical nanostructure we have shown the proof-of-principle demonstration of a ‘continuous-flow’ water treatment system to decompose known organic pollutants in water, as well as render common waterborne bacteria non-viable.

    We have studied synthesis of colloidal quantum dots (QD), and show size, morphology and composition tailored nanocrystals for CdE (E=S, Se, Te) compositions. We have studied the influence of crystal growth habits of the nanocrtsyals on the final morphology. Furthermore we have synthesized core-shell, CdSe-CdS QDs with spherical and tetrahedral morphologies by varying the reaction conditions. We show that these core-shell quantum dots show quasi-type II characteristics, and demonstrate with I-V measurements, the spatial localization of the charge carriers in these hetero-nanocrystals. For this purpose, we developed hybrid materials consisting of the core-shell quantum dots with electron acceptors (ZnO nanowires) and hole acceptors (polymeric P3HT nanofibers).

    In addition we have also compared the synthesis reaction when carried out with conventional heating and microwave-mediated heating. We find that the reaction is enhanced, and the yield is qualitatively better when using microwave induced heating.

  • 125.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Photochemical and Photoelectric Applications of II-VI Semiconductor Nanomaterials2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this work we investigated fabrication of semiconductor nanomaterials and evaluated their potential for photo-chemical and photovoltaic applications. We investigated two different II-VI semiconductor nanomaterial systems; (i) ZnO oriented nanowire arrays non-epitaxially grown from a substrate; and (ii) colloidal CdTe nanotetrapods synthesized by solution-based thermal decomposition of organo-metallic precursors. In both the cases our main focus has been optimizing material synthesis for improving potential applications based on photon-electron interactions.

    We have studied the synthesis of vertically aligned ZnO nanowire arrays (NWA), by a wet chemical process on various substrates. The synthesis is based on epitaxial growth of ZnO seed-layer on a substrate in a chemical bath consisting of an aqueous solution of zinc nitrate and hexamethylenetetramine (HMT). We have suggested an additional role played by HMT during the synthesis of ZnO nanowire arrays. We have also extended this synthesis method to fabricate hierarchical nanostructures of nanofibers of poly-L-lactide acting as a substrate for the radially oriented growth of ZnO nanowires. The combination of high surface area of the nanofibrous substrate with the flexibility of the PLLA-ZnO hierarchical nanostructure enabled the proof-of-principle demonstration of a ‘continuous-flow’ water treatment system that could effectively decompose single and combination of known organic pollutants in water, as well as render common waterborne bacteria nonviable.

    We have studied another chemical synthesis that is commonly used for size controlled synthesis of colloidal quantum dots, which was modified to obtain anisotropic nanocrystals mainly for CdE (E=S, Se, Te) compositions. In this work we demonstrate by use of oleic acid (instead of alkylphosphonic acids) it is possible to synthesize CdTe and CdSe nanotetrapods at much lower temperatures (~180 ºC) than what is commonly reported in the literature, with significantly different  formation mechanism in the low-temperature reaction.

    Finally, we have performed preliminary photoconduction measurements with CdTe nanotetrapods using gold ‘nanogap’ electrodes fabricated in-house, and obtain up to 100 times enhancement in current levels in the I–V measurements under illumination with a white light source.

  • 126.
    Sugunan, Abhilash
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Guduru, Veerendra K.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Uheida, Abdusalam
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    A ‘Continuous flow’ Photochemical Water Treatment System Based on Radially Oriented ZnO Nanowires on Flexible Poly-L-Lactide NanofibersManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Several oxide ceramics, notably ZnO and TiO2 are known to catalyze decomposition of organic molecules in water under ultra-violet irradiation. Here we describe fabrication of highly flexible ZnO-based hierarchical nanostructure obtained by growing radially oriented ZnO nanowires on poly-L-lactide nanofibers. Utilizing the flexibility and high surface area of polymeric nanofibers as novel ‘substrate’ for growth of the photochemically active ZnO nanowires we show a proof-of-principle demonstration of a ‘continuous flow’ water treatment set-up. We have monitored photocatalytic decomposition of known organic pollutants, such as methylene blue, monocrotophos and diphenylamine under illumination with ultraviolet light using this highly flexible hierarchical nanostructure.

  • 127.
    Sugunan, Abhilash
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Guduru, Veerendra K.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Uheida, Abdusalam
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Radially Oriented ZnO Nanowires on Flexible Poly-L-Lactide Nanofibers for Continuous-Flow Photocatalytic Water Purification2010Ingår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 93, nr 11, s. 3740-3744Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several oxide ceramics, notably ZnO and TiO2 are known to catalyze decomposition of organic molecules in water under ultraviolet (UV) irradiation. Here we describe fabrication of highly flexible ZnO-based hierarchical nanostructure obtained by growing radially oriented ZnO nanowires on poly-L-lactide nanofibers. Utilizing the flexibility and high surface area of polymeric nanofibers as novel substrate for growth of the photochemically active ZnO nanowires we show a proof-of-principle demonstration of a continuous flow water treatment setup. We have monitored photocatalytic decomposition of known organic pollutants, such as methylene blue, monocrotophos, and diphenylamine under illumination with UV light using this highly flexible hierarchical nanostructure.

  • 128.
    Sugunan, Abhilash
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Jafri, S. Hassan M.
    Qin, Jian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Blom, Tobias
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Leifer, Klaus
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Low-temperature synthesis of photoconducting CdTe nanotetrapods2010Ingår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 20, nr 6, s. 1208-1214Artikel i tidskrift (Refereegranskat)
  • 129.
    Sugunan, Abhilash
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Zhao, Yichen
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Mitra, Somak
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Dong, Lin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Li, Shanghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Marcinkevicius, Saulius
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Synthesis of tetrahedral quasi-type-II CdSe-CdS core-shell quantum dots2011Ingår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, nr 42, s. 425202-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Synthesis of colloidal nanocrystals of II-VI semiconductor materials has been refined in recent decades and their size dependent optoelectronic properties have been well established. Here we report a facile synthesis of CdSe-CdS core-shell heterostructures using a two-step hot injection process. Red-shifts in absorption and photoluminescence spectra show that the obtained quantum dots have quasi-type-II alignment of energy levels. The obtained nanocrystals have a heterostructure with a large and highly faceted tetrahedral CdS shell grown epitaxially over a spherical CdSe core. The obtained morphology as well as high resolution electron microscopy confirms that the tetrahedral shell have a zinc blende crystal structure. A phenomenological mechanism for the growth and morphology of the nanocrystals is discussed.

  • 130.
    Tafti, Mohsen Yakshi
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Saleemi, Mohsin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Toprak, Muhammet S
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Johnsson, Mats
    Stockholm University.
    Jacquot, Alexandre
    Jägle, Martin
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Fabrication and characterization of nanostructured thermoelectric FexCo1-xSb32015Ingår i: Open Chemistry, E-ISSN 2391-5420, Vol. 13, nr 1, s. 629-635Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel synthesis route for the fabrication of p-type nanostructured skutterudite, FexCo1-xSb3 in large quantity is reported. This scalable synthesis route provides nano-engineered material with less impact on the environment compared to conventional synthesis procedures. Several Fe substituted compositions have been synthesized to confirm the feasibility of the process. The process consists of a nano-sized precursor fabrication of iron and cobalt oxalate, and antimony oxides by chemical co-precipitation. Further thermochemical processes result in the formation of iron substituted skutterudites. The nanopowders are compacted by Spark Plasma Sintering (SPS) technique in order to maintain nanostructure. Detailed physicochemical as well as thermoelectric transport properties are evaluated. Results reveal strongly reduced thermal conductivity values compared to conventionally prepared counterparts, due to nanostructuring. P-type characteristic was observed from the Seebeck measurements while electrical conductivity is high and shows metallic behavior. The highest TE figure of merit of 0.25 at 800 K has been achieved, which is strongly enhanced with respect to the mother compound CoSb3. This suggests the promise of the utilized method of fabrication and processing for TE applications with improved performance.

  • 131. Thaler, Marlene
    et al.
    Roy, Soumen
    Qin, Jian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Bitsche, Mario
    Glueckert, Rudolf
    Fornara, Andrea
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Salvenmoser, Willi
    Rieger, Gunde
    Visualization and Analysis of Superparamagnetic Ferrogels in the Inner Ear by Light Microscopy and Energy Filtred TEM: a promising approach for advanced local drug deliveryIngår i: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818Artikel i tidskrift (Övrigt vetenskapligt)
  • 132.
    Thaler, Marlene
    et al.
    Carl Zeiss NTS GmbH.
    Roy, Suomen
    Medical University of Innsbruck.
    Fornara, Andrea
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Bitsche, Mario
    Medical University of Innsbruck.
    Qin, Jian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Salvenmoser, Willi
    University of Innsbruck.
    Rieger, Gunde
    Medical University of Innsbruck.
    Schrott Fischer, Anneliese
    Medical University of Innsbruck.
    Glueckert, Rudolf
    Medical University of Innsbruck.
    Visualization and Analysis of Superparamagnetic Iron Oxide Nanoparticles in the Inner Ear by Light Microscopy and Energy Filtered TEM2011Ingår i: Nanomedicine: Nanotechnology, Biology, and Medicine, ISSN 1549-9634, Vol. 7, nr 3, s. 360-369Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanoparticles as potential carriers for local drug transfer are an alternative to systemic drug delivery into the inner ear. We report on the first in vitro tests of a new ferrogel consisting of superparamagnetic iron oxide nanoparticles (SPIONs) and a Pluronic (R) F127 (PF127) copolymer. Pluronic copolymers possess a unique viscosity-adjustable property that makes PF127 gels easy to handle compared to conventional cross-linked hydrogels. This ferrogel was successfully tested in cadaver human temporal bones as well as in organotypic explant cultures of mouse inner ears. SPIONs were identified by light microscopy and localized with different imaging modes in energy-filtered transmission electron microscopy. Our approach shows a promising possibility to use iron oxide nanoparticles, which are suitable for visualization and characterization at both the light- and electron-microscopic levels.

    From the Clinical Editor: The authors report the first in vitro tests of a new ferrogel consisting of superparamagnetic iron oxide nanoparticles (SPIONs) and a Pluronic (R) F127 (PF127) copolymer for drug delivery in the inner ear, demonstrasting a promising possibility to use iron oxide nanoparticles, which are suitable for visualization and characterization at both the light- and electron-microscopic levels.

  • 133. Topkaya, R.
    et al.
    Kurtan, U.
    Baykal, A.
    Sozeri, H.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Material- och nanofysik, Funktionella material, FNM.
    Polymer Assisted Co-precipitation Synthesis and Characterization of Polyethylene Glycol (PEG)/CoFe2O4 Nanocomposite2013Ingår i: Journal of Inorganic and Organometallic Polymers and Materials, ISSN 1574-1443, Vol. 23, nr 3, s. 592-598Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyetylene glycol (PEG)/CoFe2O4 nanocomposite have been synthesized by PEG assisted co-precipitation method. The presence of PEG on the surface of CoFe2O4 nanoparticles was confirmed by Fourier transform infrared spectroscopy. Vibrating sample magnetometer measurements revealed a saturation magnetisation (M (s)) value of 90.95 emu/g, which is higher than bulk value, and coercive field (H (c)) of 862 Oe that is close to the bulk value at room temperature. The temperature dependent magnetization increases initially and then decreases with increasing temperature. This anomality is attributed to the decrease of B sublattice magnetization more rapidly than A sublattice magnetization. The M (r)/M (s) values lower than theoretical value of 0.5 suggests that the PEG/CoFe2O4 nanocomposite has effective uniaxial anisotropy according to the Stoner-Wohlfarth model. Enhanced magnetic properties (higher M (s) and bulk-like H (c) value) make the PEG/CoFe2O4 nanocomposite a promising candidate for high density magnetic recording media.

  • 134.
    Toprak, Muhammet S.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Darab, Mahdi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Syvertsen, Guttorm Ernst
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Synthesis of nanostructured BSCF by oxalate co-precipitation - As potential cathode material for solid oxide fuels cells2010Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 35, nr 17, s. 9448-9454Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    BaxSr1-xCoyFe1-yO3 (BSCF) cathode material for solid oxide fuel cells (SOFC) was synthesized in nanocrystalline form by a novel chemical alloying approach. Thermodynamic modeling has been performed using Medusa software for obtaining the optimum conditions for the fabrication of a precursor with the desired composition. Precursor powder was then calcined and annealed to produce the final mixed oxide BSCF composition. The thermal properties, phase constituents, microstructure and elemental analysis of the samples were characterized by TGA, XRD, SEM and EDS techniques respectively. Spark Plasma Sintering (SPS) has been used at 1080 degrees C and under 50 MPa pressure to obtain the pellets of BSCF with preserved nanostructure and rather high compaction density for electrical conductivity measurements. The results show that the powders have cubic perovskite-type structure with a high homogeneity. Finer resultant powder, compared to earlier reports, and SPS sintered BSCF with nanosized grains exhibited a significantly higher electrical conductivity up to 900 degrees C. Specific conductivity values have been measured in air and N-2 and the maximum of 63 5 cm(-1) at 430 degrees C in air and 25 S cm(-1) at 375 degrees C in N-2 correspondingly show twice as much as conventional BSCF implying a high pledge for nano-BSCF as cathode material in intermediate-temperature SOFC. This is due to the lower interfacial resistance of preserved nanograins by the use of SPS sintering. Presented co-precipitation method is easy to handle and has a high promise to synthesize BSCF at large-scale for IT-SOFCs.

  • 135.
    Toprak, Muhammet S
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Seisenbaeva, Gulaim A.
    Kessler, Vadim G.
    ANNEX: Synthesis of Nanomaterials2012Ingår i: Adverse Effects of Engineered Nanoparticles / [ed] Bengt Fadeel, Antonio Pietroiusti, and Anna Shvedova, Academic Press, 2012Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 136.
    Toprak, Muhammet S.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Vogt, Carmen
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Active Cooperative Assemblies Towards Nanocomposites2009Ingår i: ADVANCES IN MATERIAL DESIGN FOR REGENERATIVE MEDICINE, DRUG DELIVERY AND TARGETING/IMAGING    / [ed] Shastri VP; Lendlein A; Liu L; Mikos A; Mitragotri S, 2009, Vol. 1140, s. 197-202Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work reports on the fabrication of novel type of assemblies bearing magnetic nanoparticles and inorganic shells prepared via a biomimetic route of complex coacervation. Magnetic nanoparticles fabricated under controlled conditions were surface modified with polyacrylic acid (PAA). Subsequently, PAA spontaneously formed spherical assemblies in contact with certain ions, such as Ca2+. The stability of these microspheres against environmental alterations such as pH, ionic strength, and dilution was increased through cross-linking. Ethylene diammine (EDA) was used as a cross-linker, which resulted in mechanically stabilized system that does not show sensitivity towards the external pH values. Important parameters for the formation of these coacervates as well as mechanism of formation and cross-linking have been evaluated by FTIR analysis. The cooperative assemblies are still active for further reaction and were used for the growth of an inorganic aluminum oxide shell. SEM analysis of these spheres showed that the structures are hollow with a large interior volume. A biocompatible outer surface combined with the magnetic functionality is very important for the targeted drug delivery devices for biomedical applications.

  • 137. Unal, B.
    et al.
    Durmus, Z.
    Baykal, A.
    Sozeri, H.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Alpsoy, L.
    L-Histidine coated iron oxide nanoparticles: Synthesis, structural and conductivity characterization2010Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 505, nr 1, s. 172-178Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    L-Histidine capped iron oxide nanoparticles (HCIO) have been synthesized in one pot in the presence of L-histidine. The final product was analyzed for composition, microstructure, ac-dc conductivity performance as well as dielectric permittivity. Results revealed that magnetic nanoparticles are maghemite (or magnetite) and L-histidine is covalently bonded to the nanoparticle surface via carboxyl groups. Thermal analysis revealed that magnetic nanoparticles showed catalytic effect that caused an early degradation/decomposition of the L-histidine capping. Near spherical morphology was assessed by TEM and particle size calculated from TEM analysis and crystallite size calculated from XRD analysis reveal single crystalline nature of iron oxide NPs. Magnetic measurements reveal the superparamagnetic character of the nanoparticles, hence the nanocomposite. The ac conductivity showed a temperature-dependent behavior at low frequencies and temperature independent behavior at high frequencies which is an indication of ionic conductivity. The dc conductivity of the nanocomposites is found to obey the Arrhenius plot with activation energy of 0.934 eV. Analysis of electrical modulus and dielectric permittivity functions suggest that ionic and polymer segmental motions are strongly coupled in the nanocomposite. (C) 2010 Elsevier B.V. All rights reserved.

  • 138. Unal, B.
    et al.
    Durmus, Z.
    Baykal, A.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Sozeri, H.
    Bozkurt, A.
    Synthesis, dielectric and magnetic characteristics of poly(1-vinyl-1,2,4-triazole) (PVTri)-barium hexaferrite composite2011Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 509, nr 32, s. 8199-8206Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The production of PVTri-BaFe(12)O(19) composites was carried out by in situ polymerization of PVTri in the presence of synthesized BaFe(12)O(19) particles. Crystalline phase was determined as BaFe(12)O(19) by XRD analysis and thermal analysis revealed an inorganic content of similar to 45% in the composite. SEM and TEM analyses showed strongly agglomerated particles in the range of 200 nm to several micrometers in the composite. The dielectric function of the various temperatures showed frequency dependency in a reciprocal power law. The dissipation (or loss) of energy stored within the composite was found to obey the reciprocal rule of power law of the frequency dependency. The real part of electrical modulus formalism increased exponentially with frequency for various temperatures, reaching a constant value and finally saturated. The imaginary part showed a reciprocal power law against the applied frequency and shifted to higher frequency at elevated temperatures. Magnetization measurements revealed substantially lower saturation magnetization of the composite material as compared to the bulk barium ferrite powders, possibly due to pinning of some of the surface spins by the adsorption of the PVTri molecules to the surface of the BaFe(12)O(19).

  • 139. Unal, B.
    et al.
    Durmus, Z.
    Kavas, H.
    Baykal, A.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Synthesis, conductivity and dielectric characterization of salicylic acid-Fe3O4 nanocomposite2010Ingår i: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 123, nr 1, s. 184-190Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the synthesis of water dispersible salicylic acid -Fe3O4 nanocomposites via a co-precipitation route by using Fe(III) and Fe(II) chloride salts, and salicylic acid. Crystalline phase was identified as Fe3O4 and the crystallite size was obtained as 13 +/- 6 nm from X-ray line profile fitting. As compared to the particle size of 20 nm obtained from TEM analysis these particles show polycrystalline nature. The capping of salicylic acid around Fe3O4 nanoparticles was confirmed by FTIR spectroscopy, the interaction being via bridging oxygens of the carboxylate and the nanoparticle surface. ac and dc conductivity measurements performed on the nanocomposite revealed semiconductor characteristics and varying trends with temperature due to reorganization of the nanocomposite. Permittivity measurements showed increasing dielectric constant with increasing temperature as expected from semiconductors. Analysis of electrical modulus and dielectric permittivity functions suggest that ionic and polymer segmental motions are strongly coupled in the nanocomposite. (C) 2010 Elsevier B.V. All rights reserved.

  • 140. Unal, B.
    et al.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Durmus, Z.
    Sozeri, H.
    Baykal, A.
    Synthesis, structural and conductivity characterization of alginic acid-Fe3O4 nanocomposite2010Ingår i: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 12, nr 8, s. 3039-3048Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Alginic acid-Fe3O4 nanocomposite is synthesized by the precipitation of Fe3O4 in the presence of alginic acid (AA). Structural, surface, morphological, thermal and electrical transport properties of the nanocomposite were performed by XRD, FT-IR, TEM-SEM, TGA and conductivity measurements respectively. FT-IR analysis revealed that Fe3O4 NPs are strongly capped with AA and TGA analysis showed that nanocomposite have 80% of Fe3O4 content. TEM analysis of Fe3O4 NPs show an average particle size of 9.5 nm, and upon nanocomposite formation with AA these particles are observed to form aggregates of similar to 150 nm. The frequency-dependency of the AC conductivity show electrode polarization effect. Analysis of electrical modulus and dielectric permittivity functions suggest that ionic and polymer segmental motions are strongly coupled. DC electrical conductivity is strongly temperature dependent, and is classified into three regions over a limited temperature range of up to 100 A degrees C.

  • 141. Uzun, K.
    et al.
    Cevik, E.
    Senel, M.
    Sozeri, H.
    Baykal, A.
    Abasiyanik, M. F.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Covalent immobilization of invertase on PAMAM-dendrimer modified superparamagnetic iron oxide nanoparticles2010Ingår i: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 12, nr 8, s. 3057-3067Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, polyamidoamine (PAMAM) dendrimer was synthesized on the surface of superparamagnetite nanoparticles to enhance invertase immobilization. The amount of immobilized enzyme on the surface-hyperbranched magnetite nanoparticle was up to 2.5 times (i.e., 250%) as much as that of magnetite nanoparticle modified with only amino silane. Maximum reaction rate (V (max)) and Michaelis-Menten constant (K (m)) were determined for the free and immobilized enzymes. Various characteristics of immobilized invertase such as; the temperature activity, thermal stability, operational stability, and storage stability were evaluated and results revealed that stability of the enzyme is improved upon immobilization.

  • 142. Vallhov, H.
    et al.
    Qin, Jian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Johansson, S.
    Muhammed, Mamoun Ali
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Gabrielsson, S.
    Scheynius, A.
    The effect of gold nanoparticles on dendritic cells2006Ingår i: 2006 NSTI Nanotechnology Conference and Trade Show: NSTI Nanotech 2006 Technical Proceedings, 2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    Gold is recognized as one of the most biocompatible and stable materials, and has been used for many years as a medical agent, among others in the form of salt for the treatment of rheumatoid arthritis [1]. More recent biological applications have been focusing on using gold nanoparticles for drug and gene delivery [2], or as a photothermal agent causing highly localized heating applicable in cancer therapy [3]. There is however very little information available concerning what influence such particles have on the immune system, e.g. on dendritic cells (DCs). DCs are present throughout the human body but are particularly localized at antigen-exposed sites, such as the skin. They are the most efficient type of antigen presenting cells having a capacity both to initiate primary and secondary immune responses, by expressing cytokines, MHC and co-stimulatory molecules such as CD80, CD83 and CD86 [4-5]. DCs decide whether an immune response should be initiated and are able to affect the development of T-helper cells into Treg-, Th1- or Th2-cells depending on their cytokines produced and their expression of co-stimulatory molecules [6]. We addressed the question whether spherical gold nanoparticles of 6 nm in diameter affect DCs, looking at morphology, viability, expression of cytokines and of co-stimulatory and antigen presenting molecules. This was assessed by using human monocyte derived DCs (myeloid DCs) and peripheral blood mononuclear cells from healthy blood donors together with gold nanoparticles [7], and various techniques including light microscopy, flow cytometry and ELISpot. After having overcome aggregation problems of gold nanoparticles by stabilizing with human serum albumin (HSA) and developed methods to produce nanoparticles with low lipopolysaccharide (LPS) contamination, experiments revealed that both morphology and viability were not affected by the gold nanoparticles. The expression of CD80, CD83, CD86 and MHC class II was only to a minor degree up-regulated after 6 and 24 h, and CD40 and MHC class I was not affected, which indicates biocompatibility of gold nanoparticles. This is further supported by low or no expression of the cytokines IL-10, IL-12 and IFN-alpha. HSA by itself did not have an effect on the DCs. In conclusion, gold nanoparticles of 6 nm in diameter are highly unlikely to initiate a danger signal to the immune system through the dendritic cells, and have therefore the potential to be used as inert carriers in biomedical applications.

  • 143. Vallhov, Helen
    et al.
    Qin, Jian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Johansson, Sara M.
    Ahlborg, Niklas
    Muhammed, Mamoun A.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Scheynius, Annika
    Gabrielsson, Susanne
    The importance of an endotoxin-free environment during the production of nanoparticles used in medical applications2006Ingår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 6, nr 8, s. 1682-1686Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated the effect of spherical gold nanoparticles on immature dendritic cells (DCs). Conventionally produced nanoparticles had a maturating effect on the DCs-a result of lipopolysaccharide (LPS) contamination. By modification of the production process, low-LPS particles were obtained, which had practically no effect on phenotypic maturation or cytokine production of the DCs. Our findings emphasize the importance of high purity in the production of nanoparticles, since possible contaminants may interfere with the assessment of biological/medical effects. They also highlight that nanoparticles can function as carriers of immune modulating contaminants.

  • 144.
    Vogt, Carmen M.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Kunzmann, Andrea
    Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
    Torres, Neus Feliu
    Institute of Environmental Medicine, Karolinska Insitutet.
    Thurnherr, Tina
    Laboratory for Materials-Biology Interactoins, Swiss Federal Laboratories for Materials Testing and Research (EMPA), Gallen, Switzerland.
    Laurent, Sophie
    University of Mons-Hainaut, Belgium.
    Bridot, Jean-Luc
    University of Mons-Hainaut, Belgium.
    Müller, Robert N.
    University of Mons-Hainaut, Belgium.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Krug, Harald F.
    Laboratory for Materials-Biology.
    Fadeel, Bengt
    Institute of Environmental Medicine, Karolinska Institutet.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Biocompatibility of tuneable silica shell-magnetic core nanoparticles evaluated in vitro using primary human monocute-derived macrophagesManuskript (preprint) (Övrig (populärvetenskap, debatt, mm))
  • 145.
    Vogt, Carmen M.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Laurent, Sophie
    University of Mons-Hainaut, Belgium.
    Bridot, Jean-Luc
    University of Mons-Hainaut, Belgium.
    Müller, Robert N.
    University of Mons-Hainaut.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    High quality and tuneable silica shell-magnetic core nanoparticles2010Ingår i: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 12, nr 4, s. 1137-1147Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Obtaining small (<50 nm), monodispersed, well-separated, single iron oxide core-silica SiO2) shell nanoparticles for biomedical applications is still a challenge. Preferably, they are synthesized by inverse microemulsion method. However, substantial amount of aggregated and multicore core- shell nanoparticles is the undesired outcome of the method. In this study, we report on the production of less than 50 nm overall size, monodispersed, free of necking, single core iron oxide-SiO2 shell nanoparticles with tuneable shell thickness by a carefully optimized inverse microemulsion method. The high degree of control over the process is achieved by understanding the mechanism of core-shell nanoparticles formation. By varying the reaction time and recursor concentration, the thickness of silica layer an the core nanoparticles can be finely adjusted from to 13 nm. Residual reactions during the workup were inhibited by a combination of pH control with hock freezing and ultracentrifuging. These highquality tuneable core-shell nanocomposite particles exhibit superparamagnetic character and sufficiently high magnetization with great potential for biomedical applications (e.g. MRI, cell separation and magnetically driven drug delivery systems) either as-prepared or by additional surface modification for improved biocompatibility.

  • 146.
    Vogt, Carmen M.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Shi, J.
    Torres, N. F.
    Fadeel, B.
    Laurent, S.
    Bridot, J. -L
    Müller, R. N.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Optimised synthetic route for tuneable shell Si02@Fe304 core-shell nanoparticles2009Ingår i: Advances in material design for regenerative medicine, drug delivery, and targeting/imaging, Materials Research Society, 2009, s. 209-214Konferensbidrag (Refereegranskat)
    Abstract [en]

    Multifunctional nanoparticles (that have in their structure different components that can perform various functions) are subject of intensive research activities as they find a large variety of applications in numerous biomedical fields from enhancement of image contrast in MRI to different magnetically controllable drug delivery systems. In this study we report on the synthesis of well-separated, monodisperse single core-shell Si02@Fe304 nanoparticles with an overall diameter of ̃30 nm. The influence of stirring rate and reaction time on synthesis of tuneable shell thickness core-shell nanoparticles is reported. Particles' cell toxicity and performance as MRI contrast agents were also studied due to their promising biological applications (as contrast agents, cell labelling and separation, drug delivery systems, etc.) and results are promising in terms of MRI performance as well as having no significant cytotoxicity.

  • 147.
    Vogt, Carmen M.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Shi, Jingwen
    Institute of Environmental Medicine, Karolinska Institutet.
    Torres, Neus Feliu
    Institute of Environmental Medicine, Karolinska Institutet.
    Fadeel, Bengt
    Institute of Environmental Medicine, Karolinska Institutet.
    Laurent, Sophie
    University of Mons-Hainaut, Belgium.
    Bridot, Jean-Luc
    University of Mons-Hainaut, Belgium.
    Müller, Robert N.
    University of Mons-Hainaut.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Optimised Synthetic Route for Tuneable Shell SiO2@Fe3O4 Core-Shell Nanoparticles2009Ingår i: Materials Research Society Symposium Proceedings, 2009, Vol. 1140, s. 209-214Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Multifunctional nanoparticles (that have in their structure different components that can perform various functions) are subject of intensive research activities as they find a large variety of applications in numerous biomedical fields from enhancement of image contrast in MRI to different magnetically controllable drug delivery systems. In this study we report on the synthesis of well-separated, monodisperse single coreshell SiO2@Fe3O4 nanoparticles with an overall diameter of ~30 nm. The influence of stirring rate and reaction time on synthesis of tuneable shell thickness core-shell nanoparticles is reported. Particles’ cell toxicity and performance as MRI contrast agents were also studied due to their promising biological applications (as contrast agents, cell labelling and separation, drug delivery systems, etc.) and results are promising in terms of MRI performance as well as having no significant cytotoxicity.

     

  • 148.
    Vogt, Carmen Mihaela
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Engineered core-shell nanoparticles for biomedical applications2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The necessity for synthesis of nanoparticles with well controlled size and morphology emerged with the development in recent years of novel advanced applications especially in biomedical related fields. These applications require nanoparticles with more complex architecture such as multifunctional nanoparticles (i.e. core–shell structures) that can carry several components with different embedded functionalities. In this thesis, we developed core–shell nanoparticles (CSNPs) with finely tuned silica shell on iron oxide core as model system for advanced applications in nanomedicine such as MRI, drug delivery and hyperthermia.

    The synthesis of monodispersed, and well separated, single iron oxide core–silica (SiO2) shell nanoparticles for biomedical applications is still a challenge. Substantial amount of aggregated and multicore CSNPs are generally the undesired outcome. In this thesis, synthesis of monodispersed, free of necking, single core iron oxide-SiO2 different distinct overall size and tuneable shell thickness was performed using an inverse microemulsion method. The influence of the reaction time, hydrodynamic conditions and precursor concentration on the synthesis process and thickness of the silica layer was investigated and the process was optimised. The residual reactions during the post synthesis processing were inhibited using a combination of pH adjustment and alternating shock freezing with ultracentrifuging.

    The second part of the thesis is concerning thorough characterisation of the CSNPs with different shell thickness. The non-aggregated tuneable shell CSNPs maintained the superparamagnetic character of the cores with high magnetisation, showing great potential for their applications in nanomedicine. Magnetic measurements and relaxivity tests were performed and the comparison of the CSNPs with commercial products revealed the fact that relaxation time ratios (r2/r1) obtained are higher than those of the commercially available MRI contrast agents which indicates a better T2 contrast.

    In the last part of the thesis the in-vitro toxicity investigation results are reported. For the investigation of cytotoxicity (3- 4, 5-dimethyldiazol-2-yl)-2, 5 diphenyl-tetrazolium bromide (MTT) assay was performed and the secretion of pro-inflammatory cytokines TNF-α and IL-6 was determined using enzyme-linked immunosorbent assay (ELISA). The cells were exposed to a wide range of concentrations of nanoparticles (between 0.5 μg/ml to 100 μg/ml). The cell toxicity results indicated no severe toxic effects on human monocyte-derived macrophages (HMDM) as model system. The internalisation of the nanoparticles by HMDM was monitored using transmission electron microscopy (TEM).

    The CSNPs have the capacity of forming stable colloidal dispersions at physiological pH, with desired magnetic properties, low toxicity, and the potential for further functionalisation via surface modification of the silica shell or by adding new components (i.e. quantum dots, therapeutics). These characteristics make them highly promising for drug delivery, medical imaging, hyperthermia, magnetic cell marking and cell separation as well as many other biomedical applications.

     

  • 149.
    Wahlberg, Sverker
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Nanostructured Tungsten Materials by Chemical Methods2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Tungsten based-materials are used in many different technical fields, particularly in applications requiring good temperature and/or erosion resistance. Nanostructuring of tungsten alloys and composites has the potential to dramatically improve the materials’ properties, enhancing the performance in present applications or enabling totally new possibilities. Nanostructured WC-Co composites have been the focus of researchers and industries for over two decades. New methods for powder fabrication and powder consolidation have been developed. However, the fabrication of true nanograined WC-Co materials is still a challenge. Nanostructured tungsten composites for applications as plasma facing materials in fusion reactors have in recent years attracted a growing interest. This Thesis summarizes work on the development of chemical methods for the fabrication of two different types of nanostructured tungsten based materials; WC-Co materials mainly aimed at cutting tools applications and W-ODS composites with rare earth oxide particles, intended as plasma facing materials in future fusion reactors. The approach has been to prepare powders in two steps: a) synthesis of uniform powder precursors containing ions of tungsten and the doping elements by co-precipitation from aqueous solutions, and b) further processing of the precursors into W or WC based nano-composite powders.

    Highly homogenous W and Co containing powder precursors for WC-Co composites were prepared via two different routes. Keggin-based precursors ((NH4)8[H2Co2W11O40]) with agglomerates of sizes up to 50 μm, were made from sodium tungstate or ammonium metatungstate and cobalt acetate. The powder composition corresponded to 5.2 % Co in the final WC-Co composites. In a second approach, paratungstate-based precursors (Cox(NH4)10-2x[H2W12O42]) were prepared from ammonium paratungstate (APT) and cobalt hydroxide with different compositions corresponding to 3.7 to 9.7 % Co in WC-Co. These particles had a plate-like morphology with sides of 5-20 μm and a thickness of less than 1 μm. Both precursors were processed and sintered into highly uniform microstructures with fine scale (<1μm). The processing of paratungstate-based precursors was also further investigated. Nanostructured WC-Co powders with grains size of less than 50 nm by decreasing processing temperatures and by applying gas phase carburization.

    W-ODS materials were fabricated starting from ammonium paratungstate and rare earth elements (Y or La). Paratungstate-based precursors were prepared with different homogeneity and particle sizes. The degree of the chemical uniformity varied with the particle size from ca 1 to 30 μm. Tungsten trioxide hydrate-based precursors made from APT and yttrium nitrate under acidic conditions had dramatically higher homogeneity and smaller particle size. The crystallite size was decreased to a few nanometers. These precursors were further processed to composite nanopowder and sintered to a nanostructured W-1.2%Y2O3 composite with 88% relative density.

    In summary, APT can be converted to highly homogenous powder precursors of different compositions. The transformations are carried out in aqueous suspensions as a solvent mediated process, in which the starting material dissolves and the precursor precipitates. Powders with fine scale morphologies are obtained, e.g. plate-like particles with thickness less than 1 μm or spherical particles with size of a few nanometers. These precursors were processed further in to nano-sized composite powders and sintered to highly uniform tungsten composites with fine microstructures.

  • 150.
    Wahlberg, Sverker
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Yar, Mazher Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Abuelnaga, Mohammad Omar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Salem, Handi G.
    Johnsson, Mats
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Fabrication of Nanostructured W-Y2O3 Materials by Chemical Methods2012Ingår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, nr 25, s. 12622-12628Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel method for the fabrication of highly uniform oxide dispersion-strengthened (ODS) materials made by chemical processing is presented. The powders are fabricated by a two-step route starting with a chemical synthesis at room temperature, producing nanocrystalline yttrium doped tungsten trioxide hydrate precursor powders. Thermogravimetric analysis with evolved gas analysis revealed the presence of ammonium nitrate in the precursors. The second step is the reduction of the precursor in a hydrogen atmosphere at 600 and 800 degrees C. The reduced powders, containing W-1.2%Y2O3, showed two types of tungsten particles, cube-shaped with a size less than 250 nm and finer particles (<50 nm) of both spherical and cubic shape. The powder was consolidated by spark plasma sintering at 1100 degrees C, producing a bulk material with a relative density of 88%. Characterization of the sintered materials by high resolution scanning electron microscopy revealed a uniform microstructure with tungsten grains of less than 300 nm and nanosized oxide particles uniformly dispersed at the tungsten grain boundaries, as well as inside the tungsten grains. Experimental determination of the elastic properties was conducted by nanoindentation tests and fracture toughness was studied by radial indentation cracking.

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